A method of this type is known from Dutch laid-open patent application No. 1025774 in the name of the present Applicant. In this known method, a first resist layer of photosensitive resist material is applied to one side of the protective film, and this resist layer is then dried. Next, an additional resist layer is applied to this first resist layer, after which the screen is pressed into the additional resist layer, with that side of the additional resist layer on the protective film which faces the screen still being wet. In an alternative method described in the above application, the screen is pressed directly into the resist layer after this resist layer has been applied to the relevant side of the protective film; once again, the side of the resist layer to which the screen is applied needs to be wet. Therefore, this known base material comprises a screen, on one side of which a resist layer with a protective film on it is provided. The protective film has the function of protecting the resist layer during storage, transport and if desired rolling and unrolling of the base material. The result of this known method is that the surface of the resist layer on the side of the protective film has a smoothness which is better than the known base material which is marketed under the trade name “Screeny Siebdruckplatten” by Gallus Ferd. Rusch AG.
When the base material is used for screen-printing, first of all the protective film is removed from the base material. The resist layer is then exposed according to a defined pattern, developed and if appropriate (thermally) cured. The unexposed, uncured parts of the resist layer are removed, so that the screen is uncovered in the regions formed in this way. The base material which has been prepared in this way functions as a stencil in screen-printing. During screen-printing, that side of the stencil which is provided with resist faces towards the substrate that is to be printed. The uncoated side of the stencil comes into contact with the squeegee.
Now, it has been found that for some screen-printing applications, there is a demand for a base material which is coated and protected on one side and in which the screen openings have a high filling level of resist material.
Furthermore, it has been found that when using the base material described in the abovementioned Dutch patent application on the basis of an electroformed screen made from nickel, after the photoresist layer has been developed and cured, there may be occasional weak spots with only moderate adhesion to the screen. These weak spots in the base material can have an adverse effect on the printing quality during screen-printing. The occurrence of these sporadic weak spots occurs in particular at the positions where the resist layer has penetrated less far into the screen, for example as a result of inclusions of air caused by the capillary action of the screen openings, and so-called pinholes.